Spark source mass spectrometers and sample insertion probe therefor

ABSTRACT

A mass spectrometer with an insertion probe for holding and inserting a sample through a vacuum lock. Means are provided for cleaning the samples.

United States Patent London, England Mir. 2], 1966 Great Britain[2,371/66 3.368.10l 2/1968 Romzmriel|i\l..............v

[32] Priority Pnmary ExammerArch1e R. Borchelt I3 I} AssistantExaminer-A. L. Birch Allomey-Watls. Hoflman, Fisher 8; Heinke [54] SPARKSOURCE MASS SPECTROMETERS AND SAMPLE INSERTION PROBE THEREFOR 35 Claims,5 Drawing Figs.

ABSTRACT: A mass spectrometer with an insertion probe for holding andinserting a sample through a vacuum lock. Means are provided forcleaning the samples.

In, I 11/ mv mmm PAIENTH] JUL27 |97I SHEET 1 8F 2 INVENTOR. JOHN 5TEWA2THEATH ATTORNEYS.

PATENTED JIJLZTIHI SHEEI 2 0F 2 Fig. 3

Fig. 5

4 TTOENE Y8.

SPARK SOURCE MASS SPECTROMETERS AND SAMPLE INSER'IION PROBE THEREFORCROSS-REFERENCE TO RELATED APPLICATIONS 1. Application Ser. No. 460,392,entitled Mass Spectrometer sealed Vacuum Lock," now U.S. Pat. No.3,440,4l7, issued Apr. 22, I969 invented by John Stewart Heath.

BACKGROUND OF INVENTION 1. Field of the Invention The invention relatesto ionization sources for mass spectrometers and more particularly to anovel insertion probe, novel cooperating structure for causingionization of material, and to a novel method of operating a massspectrometer.

2. Description of the Prior Art In mass spectrometers of the type inwhich ionization is accomplished with an electron beam, devices haveexisted for introducing samples into an ion source chamber for analysiswithout destroying the vacuum in the ionization chamber. Thus, thedesirability of causing as little disturbance as possible to the highvacuum existing within the ion chamber has been recognized. One systemfor maintaining vacuum in an electron beam type mass spectrometer isdescribed and claimed in U.S. Pat. No. 3,l58,740 issued Nov. 24, 1964 toR. D. Craig et al. under the title Mass Spectrometer Sample lnsertionDevices. While the problems attendant to destroying the source vacuumhave been met and solved Sealed mass spectrometers with electron beamsources, with prior sparktype ion sources, when the solid sample isplaced in an ion source chamber, the chamber is opened to the atmosphereand air is permitted to enter the chamber.

When a chamber is opened to the atmosphere, in addition to therelatively apparent problem of destroying the existing vacuum, otherundesirable conditions are produced within the chamber. One undesirablecondition is that contaminating molecules of such materials as certaingases and water become attached to the surfaces within the chamber by aprocess known as adsorption. When the vacuum is reestablished, thesecontaminating molecules are released to a certain extent and limit thevacuum that can thereafter be attained. Removal of these contaminatingmolecules and consequent reduction in their partial pressure can beachieved only by pumping for long periods or by raising the temperatureof the chamber enclosure.

A reduction in the partial pressure of the contaminating molecules offoreign matter has been found to be necessary for at least two reasons.First, it is necessary to have a low partial pressure of residual gasesin the analyzer portion of the mass spectrometer to permit theunobstructed passage of ions without collision with gaseouscontaminating foreign molecules. These collisions are undesirable sincethey tend to scatter the ions and thus reduce the resolving power andaccuracy of the instrument. Second, a-low partial pressure ofcontaminating foreign molecules of oxygen and water vapor is necessaryin the ion source chamber in order that ions of oxygen originating fromthe sample material will not be masked by ions of oxygen originatingfrom stray molecules of residual foreign gases. it is often desirable todetect small traces of oxygen in solid material since it is known thatthe properties of many materials are sensitive to concentrations ofoxygen of less than one part in one million.

Another problem with prior mass spectrometers is that the solid samplesoften become contaminated before being introduced into the ion sourcechamber. Normally, deconlamination of the surfaces of the samples iscarried out in a separate vacuum vessel and during transfer from thevacuum vessel to the ion source chamber the samples are oftenunavoidably contaminated both through handling and by the reformation ofsurface oxide layers resulting from contact with atmospheric oxygen.

SUMMARY OF THE INVENTION With the present invention, a mass spectrometerhas the usual evacuable ionization chamber. A probe is provided forintroducing a sample or samples for analysis into the evacuated chamber.Samples are introduced through a vacuum lock which permits insertion ofthe probe while maintaining a high vacuum within the ionization chamber.The probe positions each sample selectively and one at a time atcleaning and analyzing positions within the chamber.

As will become more apparent, the probe can be used to in sert eitherone sample or a pair of samples simultaneously. For purposes ofexplanation, the use of two samples will be discussed, yet it should beunderstood that a single sample can be used. This permits use of theknown techniques of either (1) establishing an are between two samplesof the same material or, (2) when desired, as when arcing is difficultbecause the sample is a crystal or the like, using a counter electrodeof gold or other relatively stable metal material and a single sample.

A cleaning electrode is mounted within the chamber for use when thesamples are mounted on the probe in its cleaning position. The cleaningelectrode is about the samples so that the samples may be etched andthereby cleaned by ion bom bardment. There is also an access to thechamber for introducing a continuous flow of an inert gas into thechamber during the etching of the samples and for removing the gas andevacuating the chamber subsequent to etching and prior to ionization ofthe samples.

After the samples have been cleaned, the probe is movable to theanalyzing position. There the samples are positioned in electrodesupports at which time the samples are in their analyzing position.After the probe has positioned the samples in their analyzing positionsthe probe is removed and a spark may be drawn between the sample and acounter electrode or between the samples to ionize the sample material.Alternatively, a laser generator mounted externally of the chamber maybe used to ionize the sample material in which case the probe need notposition the samples in the electrode nor does it need to be withdrawn.

The above-referenced U.S. Pat. No. 3,440,417 discloses an insertion lockincluding a plug for opening and closing a passageway and for providingcommunication via this passageway between an exhaust port and an ionsource chamber. An insertion probe can be moved axially in thepassageway to introduce the sample into the chamber.

With the insertion probe bearing a sample initially placed in thepassageway, the valve may be opened and a vacuum maintained within thechamber since the probe seals off the passageway. After the sample hasbeen positioned in the chamber, the probe may be withdrawn past the plugbut yet sealing off the passageway. After the plug is closed, the probemay be fully withdrawn from the passageway without materially afi'ectingthe vacuum in the chamber.

in one form of the invention, the insertion probe includes a tube havinga plate connected at one end. The plate is connected to the inner sidesof the tube so as to be aligned with the central axis of the tube andextends outwardly from the end of the tube. A control rod extendsthrough the length of the tube and has a pistonlike sealing memberconnected at the end of the control rod adjacent the plate forming afluidtight seal with the inner surface of the tube. A pair of samplepositioners are connected to the pistonlike sealing member. Thepositioners are arranged in staggered fashion on opposite sides of theplate and extending outwardly from the tube opening parallel to the axisof the tube. A pair of pins are mounted in staggered fashion on oppositesides of the plate adjacent and on opposite sides of the samplepositioners. Each sample holder has a slot in its side. The pins areeach disposed in an associated one of the slots with the slots facing inopposite directions away from the adjacent and associated one of thesample positioners. Samples are mounted on the ends of the sampleholders which ends are the ends furthest from the tube.

At the end of the control rod remote from the samples, a portion of thecontrol rod extends from the tube so that the rod may be rotatedmanually or otherwise. The tube has a control slot formed near this endof the tube and a key connected to the control rod is adapted to travelin the control slot for guiding the movement of the sample positioners.The control slot has a portion aligned parallel to the axis of the tube,a second portion aligned somewhat transverse to the axis, and anotherportion aligned parallel to the axis of the tube and extending in anopposite direction from the other parallel portion.

In the form of the invention wherein the sample is ionized by a laserbeam, the sample remains mounted at the end of the insertion probe andthe laser beam originates from a laser generator external of theionization chamber.

Accordingly, the principal objects of the present invention are toprovide a novel and improved mass spectrometer including structure formaintaining a vacuum in the source when a sample is inserted, novelstructure for cleaning a sample in an evacuated chamber, a novel sampleinsertion device, and a novel method of operating a mass spectrometer.

DESCRIPTION OF THE DRAWINGS FIG. I shows a novel spark-type ion sourcein cross section;

FIG. 2 is a detailed view of the end ofthe insertion probe for holdingthe samples;

FIG. 3 is a view of the right side of the end of the insertion probeshown in FIG. 2;

FIG. 4 is a view of a sample holder in rotated position and anaccompanying sample positioner', and,

FIG. 5 is a cross-sectional view of an alternative form of the novel ionsource with laser ionization.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. I, an ionsource is shown generally at I0. The ion source I0 has an enclosure wallI4 which defines an ionization chamber 16. An insertion lock I2 isconnected to the enclosure wall 14. The insertion lock 12 is providedwith a passage 17 which communicates with the ionization chamber 16. Aninsertion probe I8 is shown inserted in the passage 17 in slidableengagement with the interior members of the insertion lock 12.

The ion source includes movable mountings 19, 20 in the form of bellowssecured to openings on opposite sides of the enclosure wall 14. A pairof insulating supports 26, 28 composed of an insulating material areconnected to the movable mountings 19, 20 respectively and are locatedwithin the ionization chamber 16. The insulating supports 26, 28 arerespectively connected to a pair of manipulators 22, 24 located outsidethe ionization chamber l6 and to a pair of slotted electrode mounts 30,32 composed of electrically conductive material located opposite oneanother within the ionization chamber 16.

A source terminal mounting 34 composed of insulating material is mountedin an aperture in the enclosure wall 14. A pair of source terminals 36,38 project through the mounting 34 and are adapted to be connected to anexternal high-voltage source. A pair of source leads 40, 42 areconnected between interior ends of the source terminals 36, 38respectively and to the electrode mounts 30, 32 respectively to providehigh voltage to the electrode mounts 30, 32 for establishing an ionizingspark when samples are carried by them.

A cleaning electrode terminal mounting 44 composed of insulatingmaterial projects through an aperture in the enclosure wall 14 near thepassage 17. A cleaning electrode terminal 46 projects through thecleaning electrode mounting 44 into the chamber [6. A lead 48 forsupplying a high-positive potential is connected to the outer end of theelectrode terminal 46 and a cleaning electrode 50 is mounted on theopposite end of the electrode terminal 46 within the ionization chamber16 adjacent the inner end of the passage l7. The cleaning electrode 50is preferably annular and has its center aligned along the longitudinalaxis of the passage 17 for at least partially surrounding a sample orsamples inserted in the chamber and thereby permitting a uniformlycleaned sample to be obtained. Cleaning is accomplished by applying 2kv.to the electrode 50 in the presence of argon so that a sample surface isbombarded by argon ions which removes surface atoms.

The insertion lock 12 includes a body 52, an end block 54 connected atthe outer end of the body 52, and a flanged, tu bular mounting member 56connected to the inner end of the body 52. The mounting member 56 isconnected to the enclo sure wall I4v The passage l7 extends through theend block 54, the body 52, and the mounting member 56 and is defined bythe inner structure of the insertion lock [2.

A pair of tubes 59, 61 are connected to the side of the body 52 anddefine ports 60, 62 respectively, each of which communicates with thepassage 17. The tubes 59, 61 may be connected to vacuum pumps. A valveplug 64 is located within the passage 17 and is preferably in the formof a rotary ball. A valve shaft 66 is positioned radially outwardly fromthe passage l7, and is connected to the valve plug 64. The shaft 66passes through a mounting cup 68 which carries seal structure to bedescribed presently. On its opposite side, the plug 64 engages anannular bearing end seal 70.

The plug 64 has a bore 72 which, in the open position shown in FIG. I,communicates with and forms a part of the passage 17. The plug 64 has atransverse bore 74 connecting the port 62 to the bore 72 to provide apath for withdrawing gases through the passage 17.

The insertion lock 12 includes a number of seals some of which areconstructed to slidably engage the outer surface of the insertion probe18 so that a high vacuum can be maintained in the ionization chamber 16while the insertion probe seals off the passage 17.

The plug 64 is clamped between two plug seals 76, 78 each of which isprovided with an opening for admitting the inser tion probe 18. The plugseal 78 engages a seal wedge 80 at the side of the plug 64 toward thechamber I6. A disc spring 82 located between the mounting member 56 andthe seal wedge 80 biases the seal wedge 80 against the plug seal 78.This biases the plug seal 78 against the inner walls of the body 52 andagainst the plug 64. Another plug seal 84 surrounds the shaft 66 andengages the shaft side of the plug 64. A sea] wedge 86 is biased againstthe plug seal 84 by a disc spring 88 located between the seal wedge 86and the cup 68. This biases the plug seal 84 against the inner walls ofthe body 52 and against the plug 64.

A sliding seal 102 including a flange I03 is positioned near the outerend of the passage 17 and around the insertion probe 18. The slidingseal may be formed of Polytetrafluoroethylene sold under the trademarkFlourosint" by Polypenco Limited, Welwyn Garden City, Herts, England.The sliding seal 102 has radially extending flange 103 which abuts theinner end of the block 54. The sliding seal I02 is identified as asliding seal because, while it remains stationary relative to theinsertion lock 12, it provides a seal against the outer surface of theinsertion probe 18 as it is shifted axially in the passage 17. Thispermits a vacuum to be maintained in the ionization chamber 16 and onlythe insertion probe 12 blocking the passage 17.

An annular seal wedge 100 is positioned next to the sliding seal I02 anda seal wedge 96 engages the seal wedge 100. A spacing tube 92 isprovided which has an opening 75 at one side communicating with the port60. The spacing tube is biased against a seal wedge by a disc spring 98which also biases the seal wedge 96 against the seal wedge 100. The biason the seal wedge I00 clamps the flange 103 of the sliding seal I02against portions of the end block 54, thus holding the sliding seal I02in place. The bias on the seal wedge 90 is applied against the seal 74to urge it into engagement with the plug 64 and the body 52.

At the exterior of the insertion lock 12, a handle 104 is con nected tothe shaft 66 for rotating the plug 64. The plug 64 is shown in an openposition in FIG. 1 for admitting the insertion probe 12. The handle 104may be locked in this open position by a locking bar 108 which isrotatably mounted on the end block 54. A collar I surrounds and issecured to an end of the locking bar I08 which passes through the endblock 54 and a pin 113 is connected to the collar 110. The pin I13engages a ring 116 mounted on the handle I04. A spring 112 biases thepin I14 against the ring I16 in the position shown. By rotating thelocking bar I08, the pin 113 will be moved clear of the ring I16 and thehandle I04 may be rotated to close the plug 64.

Referring to FIGS. 2 and 3, the sample mounting arrangement and controlmechanism of the insertion probe I8 is shown in greater detail. Theinsertion probe I8 includes a housing tube II4 ground on its outersurface to very fine cylindrical finish and has a through bore 115 alongits length. A plate 118 includes a portion disposed in the bore IIS andconnected to the interior of the tube I14 at its end adapted to beinserted within the ionization chamber I6. The plate III! also has aportion projecting from the bore I at the same end of the tube II4, andthe plate H8 is preferably aligned along the central axis of the tube114. Pivot pins I30, I3I, arranged in a staggered fashion, project fromopposite sides of the exposed portion of the plate 118. A sample holder133 having a transverse slot I34 for receiving the pin 130 is pivotallymounted on the pin I30 adjacent one side of the plate 118. Similarly, asample holder 135 (FIG. 3) having a transverse slot 134' is pivotallymounted on the pin I31 adjacent the other side of the plate I18. Beforeremoval, the sample holders I33, 135 are aligned somewhat parallel tothe longitudinal axis of the tube 114 and the open ends of the slotsI34, I34 face in opposite directions. Samples I36, 137 are respectivelymounted in ends of the sample holders I33, I35 and are secured theretoby screws I38, 138'. It is known in the art to use one sample and acounter electrode in a spark source mass spectrometer. While the members136, I37 are described as samples throughout the specification, itshould be recognized that in practice one will use one sample and apaired member. The paired member will be either a second sample or acounter electrode.

A rodlike control member 139 is positioned in the bore I15 of the tubeII4 and extends substantially the entire length of the tube I14. Aportion of the control member I39 projects from one end of the tube 114and the plate I18 projects from the opposite end. A pistonlike sealingmember I40 is connected to the control member I39 at its inner endadjacent the plate I18. The sealing member 140 slidably engages theinner surface of the tube I14 to provide a fluidtight seal and therebyprevent contaminating molecules from entering the ionization chamber 16through the tube 1 I4.

With reference to FIG. I, the tube I14 has a control slot S at its outerend. The control slot has offset portions 142, I43 aligned somewhatparallel with the longitudinal axis of the tube 114 and a transverseconnecting portion II4. A key K is connected to the control member 139and its movement is guided by the slot S.

A pair of sample positioners I45, 146 are connected to the inner side ofthe sealing member I40 adjacent the plate 118 and are arranged onopposite sides of the plate 118 for engagement with and control of thesample holders I33, 135 respectively. The sample positioners I45, 146are aligned somewhat parallel to the longitudinal axis of the tube 114and are located adjacent sides of the sample holders I33, 135respectively facing away from the open ends of the slots I34, 134',respectively.

The insertion probe 18 has a locating collar I60 around and secured tothe base of the tube IN. A pair of locating pins 161 are carried inbores 162 in the collar I60. Springs 163 normally bias the locating pins161 outwardly against annular retaining caps I64.

The locating pins, when brought into engagement with end surface I70 ofthe block 54, locate the probe 18 in its analyzing position as shown inFIG. 1.

The procedure for inserting the insertion probe I8 into the insertionlock 12 and ultimately within the ionization chamber 16 will now bedescribed. The locking bar 108 is rotated to release the handle 104 sothat the plug 64 may be rotated and closed. With the plug 64 in closedposition, a vacuum is established within the ionization chamber 16. Thesample holders and samples are mounted on the plate lIB axially in linewith the tube 114, and the insertion probe 18 is partially inserted intothe passage 58 of the insertion lock I2 until a seal is established withthe sliding seal 102. Next, the plug 64 is rotated to an open positionand the pin 113 is engaged with the ring I I6 to hold the plug in itsopen position. With the plug 64 in open position, the insertion probe 18is advanced to the cleaning position adjacent the electrode 50. In thisposition the samples are in the ionization chamber 16 and surrounded bythe cleaning electrode 50 shown in phantom in FIG. I.

A purge flow of argon is then caused to flow through tubc I75 and spaceI7 into the source region giving a pressure of about 0.02 torr. A highpositive voltage is applied to the electrode 50 to produce ahigh-voltage discharge. Ions produced in the discharge bombard thesurface of the samples 136, 137, thus etching or eroding the surface ofthe samples by a process referred to as sputtering. This erosion occursequally over the surface of the samples 136, 137 to clear off foreignmatter and any oxidized surface which may be present.

The purge flow of argon is then stopped allowing the pres sure in theionization chamber 16 to fall as the vacuum is reestablished. Theinsertion probe 18 is then advanced to the analyzing position, which isthe position of the probe shown in FIG. I, so that the sample holdersare adjacent the electrode mounts 30, 32. At this time the samples arein the position shown in FIGS. 2 and 3. The key K is at the upper end ofthe slot portion 142 so that the positioners 145, 146 maintain thesamples in that position.

The samples are then positioned in the electrode mounts 30, 32. Toaccomplish this, the control member I39 is withdrawn axially until thekey K is at the juncture of slot portions 142, I44. At this time thesample holders I33, I35 are free to rotate approximately about the pins130, 131 since the sample positioners I45, I46 and the sealing member140 are retracted to a position indicated in the dotted lines in FIG. 2.

The control member 139 is then rotated to a position in which the key Kis at the juncture of the slot portions 143, 144. This rotation causesthe positioners I45, 146 to engage and rotate the sample holders I33,135 approximately 90 from their initial axially aligned position. Thesample positioners 145, I46, the sample holders 133, I35 and the samples136, I37 are then in the positions of FIGS. I and 4 with the samplesI36, 137 aligned parallel and projecting in opposite directions. At thistime, the sample holders I33, 135 are supported by the samplepositioners I45, I46 respectively, as indicated in FIG. I and by thesolid line in FIG. 4. The manipulators 22, 24 are then moved toward thesample holders I33, 135 to a position at which the slots in theelectrode mounts 30, 32 may receive the sample holders 133, 135respectively and secure them by friction, or other means. The controlmember 139 is then retracted to a position in which the key is at thelower end of the slot portion 143 and the sample positioner I45 is atthe position shown in phantom in FIG. 4.

The probe is next shifted axially inwardly depressing the plungcrs l6Iin the bores 162 against the action of the springs 163 until the collarabuts the end surface I70. This axial shifting of the probe removes thepins 130, 131 from the slots I34, 134'. The sample holders 133, 135 arethen moved by operating the manipulators 22, 24 a sufficient amount toallow the insertion probe III to be withdrawn. The probe is partiallywithdrawn to allow closing of the plug 64 while the probe still sealsthe passage 17. The plug 64 is then closed, and the insertion probe I8is removed from the insertion lock 12.

The ionization chamber 16 is continuously vacuum pumped while thesamples are in the analyzing position. With the samples I36, 137 held inthe electrode mounts 30, 32, an arc is produced between the samples 136,137. The are may be produced by any one of the three following method:

I. A high-radio frequency voltage;

2. A high-voltage pulse followed by a low-voltage DC are;

3. A mechanical vibration arranged to cause intermittent contact betweenthe electrodes supplied from an inductive low-voltage power supply. Theelectrodes are maintained at a DC voltage such as kilovolts positivewith respect to ground and the ions formed in the are are accelerated bythis voltage to a plate (not shown) maintained at ground potential. Ionspass through a hole in this plate for analysis by the mass spectrometer.

An alternative ion source arrangement is shown in FIG. 5. in thisarrangement, the tube "4' holds an insulator support I50. A singlesample 152 is mounted on the insulator support 150. An inset structure154 is connected to the enclosure wall 14' and includes a window 156 atone endv A laser beam 157 is projected from an externally positionedlaser generator 158 through a lens 159 and through the window 156 uponthe sample 152. Procedure for using this arrangement differs from theabove-described procedure in that the tube [14' remains within theionization chamber 16' during ionization ofa single sample 152 by thelaser beam 157.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

lclaim:

1. In an ion source for a mass spectrometer the improved combinationcomprising:

a. structure defining an evacuable ionization chamber and a cleaningstation in the chamber,

b. an insertion probe for introducing at least one sample to be analyzedinto the ionization chamber while it is in an evacuated state;

c. a valve connected to the structure and having a closed position formaintaining a vacuum in the evacuable chamber; though also having anopen position for admitting the insertion probe;

d. cleaning means connected to the structure and adapted to clean asample when in the sample cleaning station;

e. ionization means carried in the chamber and defining an ionizationstation; and,

f. said probe being insertable through the valve to position a samplecarried by it selectively and one at a time in the cleaning andionization stations.

2. The device of claim 1 wherein the cleaning means is within thechamber.

3. The device of claim 2 wherein the cleaning means is a first electrodemeans which cleans the sample by etching through ion bombardment.

4. The apparatus of claim 3 wherein the first electrode means comprisesan annular electrode adapted to partially surround the sample and cleanthe sample by ion bombardment.

5. The apparatus of claim 1 wherein the ionization means is a lasergenerator positioned to direct a laser beam at the sample.

6. The apparatus of claim I wherein the insertion probe comprises:

i. a tube;

ii. a rod axially movable within the tube; and,

iii. at least one demountable sample holder connected at one end of theinsertion probe.

7. The apparatus of claim I wherein the ionization means includes atleast one electrode assembly including movable sample mounting means forholding the sample.

8. in a mass spectrometer of the spark source type, the combination of:

a. structure defining an evacuable ionization chamber;

b. an insertion probe for introducing at least one sample of material tobe analyzed and a paired member into the chamber, the insertion probeincluding means for demountably securing such sample and paired memberthereto;

c. valve means connected to the structure and having a closed positionfor maintaining a vacuum in the evacuable chamber and an open positionfor admitting the insertion probe;

d. electrode structure within the chamber for receiving the sample andthe paired member in an analyzing position; and,

e. said combination including a sample positioning means actuatable fromoutside of the ionization chamber for transferring the sample and thepaired member from the probe to the electrode structure.

9. The apparatus of claim 8 wherein the sample positioning means is partof the insertion probe and wherein the probe comprises:

i. a tube;

ii. a control rod movable within the tube;

iii. a sealing member disposed in the tube and connected to the controlrod;

iv. a plate connected to the end of the tube;

v. a pair of sample holders pivotally mounted on opposite sides of theplate;

vi. the sealing member including projecting elements each overlying aside of the plate for rotating the sample holders; and,

vii. the rod being retractable relative to the tube to retract theprojecting elements so that the sample may be removed.

10. In a mass spectrometer of the spark source type including sourcestructure defining an evacuable ionization chamber, the improvementwhich comprises:

a. an insertion lock connected to the source structure;

b. said lock having internal surfaces defining a passagewaycommunicating with the chamber and a valve for selectively opening andclosing the passageway;

c. the internal surfaces including a sealing portion, the valve beingpositioned between the sealing portion and the chamber;

d. an insertion probe including an external sealing surface of thecontour of the sealing portion and adapted for sliding movement throughsaid sealing portion while maintaining vacuum sealing engagementtherewith;

. said probe including means for carrying a sample and a paired membernear one end thereof whereby to position the sample and paired member inthe chamber when the probe projects through the passage;

f. said valve including an opening sized to receive the probe when theprobe positions the sample and paired member in the chamber;

g. said probe including structure effecting a seal within the contourgenerated by said sealing surface whereby to prevent the admission ofgases through said probe into said chamber when the probe is in thepassageway; and,

h. spark means associated with said chamber for establishing a sparkbetween the sample and the paired member when the two are in theionization chamber.

11. The spectrometer of claim 10 wherein the paired member is a secondsample.

12. The spectrometer of claim 10 wherein the paired member is a counterelectrode.

13. The mass spectrometer of claim 10 wherein the spark means includes apair of electrode members in the chamber and wherein said probe includesmanipulating means for positioning each of the samples and the pairedmember in a different one of the electrode members.

14. The method of operating a spark source mass spectrometer comprisingthe steps of a. positioning a sample on an insertion probe;

b. passing the probe through an insertion lock to position the sample inan evacuated vacuum chamber while the vacuum is maintained in thechamber;

c. cleaning the sample while in the chamber;

d. bringing the sample into contact with an electrode structure and intoan analyzing position in the chamber while still maintaining the vacuum;and,

e. establishing a spark between the sample and a paired member in thechamber.

15. The method of claim 14 wherein the step of bringing the sample intocontact with an electrode and into an analyzing position includes thestep of transferring the sample from the probe to the electrodestructure.

16. The method of claim 15 wherein the step of transferring the sampleto the electrode structure includes the step of rotating a sample holderfrom a position longitudinal of the insertion probe to a positiontransverse with respect to the axis of the insertion probe.

17. The method of claim 15 wherein the probe is partially withdrawnbefore a spark is established between the sample and a paired member.

18. The method of claim 14 wherein the step of cleaning the sampleincludes admitting a purging flow of inert gas into the chamber andthereafter reestablishing the vacuum.

[9. The method of claim 18 wherein the inert gas is argon.

20. The apparatus of claim 19 wherein the sample positioning means ispart of the insertion probe and wherein the probe comprises:

i. a tubular body;

ii. a control element disposed within the body and movablelongitudinally and rotatably relative to the body while in sealingrelationship therewith;

iii. said body having a central longitudinally extending member at oneend thereof;

iv. a sample holder mounted on said member; and,

v. means on an end of the control element adapted to contact andmanipulate the sample holder on movement of said control element toshift the sample holder from a position longitudinal of the probe to aposition transverse of the probe.

21. The method of claim 14 wherein the sample is cleaned with anelectrode and the cleaning is accomplished by etching through ionbombardment.

22. The method of claim 21 wherein the electrode is an annular electrodeand the sample is positioned at least partially within the annularelectrode when it is cleaned.

23. In a mass spectrometers of the spark source type, the combinationof:

a. structure defining an evacuable ionization chamber;

b. an insertion probe for introducing at least one sample of material tobe analyzed into the evacuated chamber, the insertion probe includingmeans for demountably securing such sample thereto;

c. valve means connected to the structure and having a closed positionfor maintaining a vacuum in the evacuable chamber and an open positionfor admitting the insertion prove;

d. electrode structure within the chamber for receiving the sample in ananalyzing position;

c. said combination including a sample positioning means actuable fromoutside of the ionization chamber for transferring the sample from theprobe to the electrode structure;

i. said sample positioning means including structure in the probe formaintaining a sample carried by the probe disposed substantiallylongitudinally of the probe during insertion and for moving the samplesupport to a position transverse of the probe after insertion; and,

g. said sample positioning means also includes movable portions of saidelectrode structure adapted to transfer a sample from the probe.

24. The combination of claim 23 wherein the sample support is moved fromits longitudinal to its transverse position by rotation of the samplesupport member.

25. The method of operating a spark source mass spec trometer comprisingthe steps of:

a. positioning a sample on an insertion probe;

b. passing the probe through an lock to position the sample in anevacuated vacuum chamber while the vacuum is maintained in the chamber;

c. rotating a sample holder from a position longitudinal of theinsertion probe to position transverse with respect to the as of theinsertion probe and bringing the sample into contact with an electrodestructure and into an analyzing position in the chamber while stillmaintaining the vacuum; and,

d. establishing a spark between the sample and a paired member in thechamber.

26. In a mass spectrometer, the improved combination comprising:

a. structure establishing an evacuable chamber and a sam ple insertionpassage communicating with the chamber;

b. ionization means establishing a sample ionization stain within thechamber and including means to ionize a sample positioned at theionization station;

c. valve means connected to the structure for selectively closing saidpassage to maintain a vacuum within the space;

d. said structure establishing a path of sample travel from external ofsaid structure through said valve means to said ionization station;

e. an insertion probe adapted to transport a sample from a positionexternal of said structure along said path to said ionization station;and,

f. cleaning means along said path and within said chamber for cleaning asample within said chamber after it has been moved along said path pastsaid valve means by the insertion probe.

27. The mass spectrometer of claim 26 wherein said cleaning meansestablishes a cleaning station between the valve means and theionization station.

28. The combination of claim 26 wherein said cleaning means includesmeans to admit a purging flow of gas after a sample has been cleaned.

29. The combination of claim 26 wherein the cleaning means includes anelectrode adapted to clean a sample by ion bombardment.

30. The device of claim 29 wherein the electrode is an annular electrodeadapted to partially surround the sample and clean the sample by ionbombardment.

31. The method of positioning a sample in a spark source massspectrometer comprising the steps of:

a. mounting a sample and a paired member on a single insertion probe;

b. inserting a probe into an insertion lock to establish a vacuum sealtherebetween;

c. opening a valve in the insertion lock and thereafter insert ing thesample and paired member into an evacuated ionization chamber by passingthe insertion probe through the valve, and,

d. thereafter establishing a spark between the sample and the pairedmember to ionize portions of the sample.

32. The method of claim 31 including the step of transferring the sampleand paired member from the probe to electrode structures within theevacuated chamber prior to establishing a spark.

33. The method of claim 31 wherein the paired member is a second sample.

34. An insertion probe comprising:

a. a tube;

b. a control rod movable within the tube;

0. a sealing member disposed in the tube and connected to the controlrod;

d. a plate connected to the end of the tube;

e. a pair of sample holders pivotally mounted on opposite sides of theplate;

f. the sealing member including projecting elements each overlaying aside of the plate for rotating the sample holders; and

g. the rod being retractable relative to the tube to retract theprojecting elements so that the sample may be removed,

35. An insertion probe comprising:

a. a tubular body;

e. means on an end of the control element adapted to con tact andmanipulate the sample holder on movement of said control element toshift the sample holder from a position longitudinal of the probe to aposition transverse of the probe.

1. In an ion source for a mass spectrometer the improved combinationcomprising: a. structure defining an evacuable ionization chamber and acleaning station in the chamber, b. an insertion probe for introducingat least one sample to be analyzed into the ionization chamber while itis in an evacuated state; c. a valve connected to the structure andhaving a closed position for maintaining a vacuum in the evacuablechamber; though also having an open position for admitting the insertionprobe; d. cleaning means connected to the structure and adapted to cleana sample when in the sample cleaning station; e. ionization meanscarried in the chamber and defining an ionization station; and, f. saidprobe being insertable through the valve to position a sample carried byit selectively and one at a time in the cleaning and ionizationstatioNs.
 2. The device of claim 1 wherein the cleaning means is withinthe chamber.
 3. The device of claim 2 wherein the cleaning means is afirst electrode means which cleans the sample by etching through ionbombardment.
 4. The apparatus of claim 3 wherein the first electrodemeans comprises an annular electrode adapted to partially surround thesample and clean the sample by ion bombardment.
 5. The apparatus ofclaim 1 wherein the ionization means is a laser generator positioned todirect a laser beam at the sample.
 6. The apparatus of claim 1 whereinthe insertion probe comprises: i. a tube; ii. a rod axially movablewithin the tube; and, iii. at least one demountable sample holderconnected at one end of the insertion probe.
 7. The apparatus of claim 1wherein the ionization means includes at least one electrode assemblyincluding movable sample mounting means for holding the sample.
 8. In amass spectrometer of the spark source type, the combination of: a.structure defining an evacuable ionization chamber; b. an insertionprobe for introducing at least one sample of material to be analyzed anda paired member into the chamber, the insertion probe including meansfor demountably securing such sample and paired member thereto; c. valvemeans connected to the structure and having a closed position formaintaining a vacuum in the evacuable chamber and an open position foradmitting the insertion probe; d. electrode structure within the chamberfor receiving the sample and the paired member in an analyzing position;and, e. said combination including a sample positioning means actuatablefrom outside of the ionization chamber for transferring the sample andthe paired member from the probe to the electrode structure.
 9. Theapparatus of claim 8 wherein the sample positioning means is part of theinsertion probe and wherein the probe comprises: i. a tube; ii. acontrol rod movable within the tube; iii. a sealing member disposed inthe tube and connected to the control rod; iv. a plate connected to theend of the tube; v. a pair of sample holders pivotally mounted onopposite sides of the plate; vi. the sealing member including projectingelements each overlying a side of the plate for rotating the sampleholders; and, vii. the rod being retractable relative to the tube toretract the projecting elements so that the sample may be removed. 10.In a mass spectrometer of the spark source type including sourcestructure defining an evacuable ionization chamber, the improvementwhich comprises: a. an insertion lock connected to the source structure;b. said lock having internal surfaces defining a passagewaycommunicating with the chamber and a valve for selectively opening andclosing the passageway; c. the internal surfaces including a sealingportion, the valve being positioned between the sealing portion and thechamber; d. an insertion probe including an external sealing surface ofthe contour of the sealing portion and adapted for sliding movementthrough said sealing portion while maintaining vacuum sealing engagementtherewith; e. said probe including means for carrying a sample and apaired member near one end thereof whereby to position the sample andpaired member in the chamber when the probe projects through thepassage; f. said valve including an opening sized to receive the probewhen the probe positions the sample and paired member in the chamber; g.said probe including structure effecting a seal within the contourgenerated by said sealing surface whereby to prevent the admission ofgases through said probe into said chamber when the probe is in thepassageway; and, h. spark means associated with said chamber forestablishing a spark between the sample and the paired member when thetwo are in the ionization chamber.
 11. The spectrometer of claim 10wherein the paired member is a second sample.
 12. The spectrometer ofclaim 10 wherein the paired member is a counter electrode.
 13. The massspectrometer of claim 10 wherein the spark means includes a pair ofelectrode members in the chamber and wherein said probe includesmanipulating means for positioning each of the samples and the pairedmember in a different one of the electrode members.
 14. The method ofoperating a spark source mass spectrometer comprising the steps of: a.positioning a sample on an insertion probe; b. passing the probe throughan insertion lock to position the sample in an evacuated vacuum chamberwhile the vacuum is maintained in the chamber; c. cleaning the samplewhile in the chamber; d. bringing the sample into contact with anelectrode structure and into an analyzing position in the chamber whilestill maintaining the vacuum; and, e. establishing a spark between thesample and a paired member in the chamber.
 15. The method of claim 14wherein the step of bringing the sample into contact with an electrodeand into an analyzing position includes the step of transferring thesample from the probe to the electrode structure.
 16. The method ofclaim 15 wherein the step of transferring the sample to the electrodestructure includes the step of rotating a sample holder from a positionlongitudinal of the insertion probe to a position transverse withrespect to the axis of the insertion probe.
 17. The method of claim 15wherein the probe is partially withdrawn before a spark is establishedbetween the sample and a paired member.
 18. The method of claim 14wherein the step of cleaning the sample includes admitting a purgingflow of inert gas into the chamber and thereafter reestablishing thevacuum.
 19. The method of claim 18 wherein the inert gas is argon. 20.The method of claim 14 wherein the sample is cleaned with an electrodeand the cleaning is accomplished by etching through ion bombardment. 20.The apparatus of claim 19 wherein the sample positioning means is partof the insertion probe and wherein the probe comprises: i. a tubularbody; ii. a control element disposed within the body and movablelongitudinally and rotatably relative to the body while in sealingrelationship therewith; iii. said body having a central longitudinallyextending member at one end thereof; iv. a sample holder mounted on saidmember; and, v. means on an end of the control element adapted tocontact and manipulate the sample holder on movement of said controlelement to shift the sample holder from a position longitudinal of theprobe to a position transverse of the probe.
 22. The method of claim 21wherein the electrode is an annular electrode and the sample ispositioned at least partially within the annular electrode when it iscleaned.
 23. In a mass spectrometers of the spark source type, thecombination of: a. structure defining an evacuable ionization chamber;b. an insertion probe for introducing at least one sample of material tobe analyzed into the evacuated chamber, the insertion probe includingmeans for demountably securing such sample thereto; c. valve meansconnected to the structure and having a closed position for maintaininga vacuum in the evacuable chamber and an open position for admitting theinsertion prove; d. electrode structure within the chamber for receivingthe sample in an analyzing position; e. said combination including asample positioning means actuable from outside of the ionization chamberfor transferring the sample from the probe to the electrode structure;f. said sample positioning means including structure in the probe formaintaining a sample carried by the probe disposed substantiallylongitudinally of the probe during insertion and for moving the samplesupport to a position transverse of the probe after insertion; and, g.said sample positioning means also includes movable portions of saidelectrode structure adapted to transfer a sample from the probe.
 24. ThecombinatioN of claim 23 wherein the sample support is moved from itslongitudinal to its transverse position by rotation of the samplesupport member.
 25. The method of operating a spark source massspectrometer comprising the steps of: a. positioning a sample on aninsertion probe; b. passing the probe through an lock to position thesample in an evacuated vacuum chamber while the vacuum is maintained inthe chamber; c. rotating a sample holder from a position longitudinal ofthe insertion probe to position transverse with respect to the as of theinsertion probe and bringing the sample into contact with an electrodestructure and into an analyzing position in the chamber while stillmaintaining the vacuum; and, d. establishing a spark between the sampleand a paired member in the chamber.
 26. In a mass spectrometer, theimproved combination comprising: a. structure establishing an evacuablechamber and a sample insertion passage communicating with the chamber;b. ionization means establishing a sample ionization stain within thechamber and including means to ionize a sample positioned at theionization station; c. valve means connected to the structure forselectively closing said passage to maintain a vacuum within the space;d. said structure establishing a path of sample travel from external ofsaid structure through said valve means to said ionization station; e.an insertion probe adapted to transport a sample from a positionexternal of said structure along said path to said ionization station;and, f. cleaning means along said path and within said chamber forcleaning a sample within said chamber after it has been moved along saidpath past said valve means by the insertion probe.
 27. The massspectrometer of claim 26 wherein said cleaning means establishes acleaning station between the valve means and the ionization station. 28.The combination of claim 26 wherein said cleaning means includes meansto admit a purging flow of gas after a sample has been cleaned.
 29. Thecombination of claim 26 wherein the cleaning means includes an electrodeadapted to clean a sample by ion bombardment.
 30. The device of claim 29wherein the electrode is an annular electrode adapted to partiallysurround the sample and clean the sample by ion bombardment.
 31. Themethod of positioning a sample in a spark source mass spectrometercomprising the steps of: a. mounting a sample and a paired member on asingle insertion probe; b. inserting a probe into an insertion lock toestablish a vacuum seal therebetween; c. opening a valve in theinsertion lock and thereafter inserting the sample and paired memberinto an evacuated ionization chamber by passing the insertion probethrough the valve, and, d. thereafter establishing a spark between thesample and the paired member to ionize portions of the sample.
 32. Themethod of claim 31 including the step of transferring the sample andpaired member from the probe to electrode structures within theevacuated chamber prior to establishing a spark.
 33. The method of claim31 wherein the paired member is a second sample.
 34. An insertion probecomprising: a. a tube; b. a control rod movable within the tube; c. asealing member disposed in the tube and connected to the control rod; d.a plate connected to the end of the tube; e. a pair of sample holderspivotally mounted on opposite sides of the plate; f. the sealing memberincluding projecting elements each overlaying a side of the plate forrotating the sample holders; and g. the rod being retractable relativeto the tube to retract the projecting elements so that the sample may beremoved.
 35. An insertion probe comprising: a. a tubular body; b. acontrol element disposed within the body and movable longitudinally androtatably relative to the body while in sealing relationship therewith;c. said body having a central longitudinally extending member at onE endthereof; d. a sample holder mounted on said member; and, e. means on anend of the control element adapted to contact and manipulate the sampleholder on movement of said control element to shift the sample holderfrom a position longitudinal of the probe to a position transverse ofthe probe.